Together with the idea that same-line extensions (cf New York commuter rail diesel islands like the NJ Coast Line and Port Jefferson line) should be merged in with the main route even though they are shuttle services at the end of the line (would the same apply to E-BART?), that gives two routes for the browser: West Ruislip - Epping and Ealing Broadway - Woodford.
So is it- Map the line like a road with branches ending when arriving on the mainline, or
- Map the line by services as two routes with a long overlap across the middle (on other routes this will escalate - the Northern line goes from 3 files to 6 and everything being at least 2 concurrencies)
Yeah so my thinking here is since we're mapping services, the mapped route should end where the train terminates. There is no such thing as a service on the NYC Subway that runs only from Ozone Park-Lefferts to Rockaway Blvd, that train runs all the way to Inwood 207th... so I made it do that.
This at least is the situation where you only have branching in one direction. Where you have branching in two directions I don't think every single possible service pattern necessarily needs to be mapped (in some cases that could get to be quite a lot) so long as every branch is included in some way. You'll see, for example, the way I've retooled LIRR, I've generally sorted the outward branches between Atlantic, Penn, Grand Central, and LIC based on which one the
majority of trains on that branch go to, with a couple branches having both Grand Central and Penn versions because the number of trains to both is near parity. There are unmapped service patterns I could add, but they'd all be 100% concurrent with already mapped patterns and thus redundant.
Re: diesel islands, I'd keep them separate if they are true islands. Wassaic, Port Washington, and Long Branch all have nonzero direct trains to Manhattan which is why I combined them with the inner, electrified portions of their respective lines. Ronkonkoma-Greenport, you may note, is still mapped separately, because there are no direct trains to Manhattan from Greenport.